17-May-2006 - The Environment
Agency is stepping-up its efforts to discover
the secrets surrounding salmon stocks on one of
England’s best known salmon rivers - the Hampshire
Avon.
The Avon is famous for its Spring
salmon. Weighing in excess of 20 lbs, these large
fish that have grown to maturity after several
winters at sea, are still found in significant
numbers in the Avon. However, the Avon has seen
a serious decline in salmon numbers and is no
longer meeting its conservation limits.
It is important rivers meet
these internationally recognised limits if they
are to support sustainable populations of salmon.
The Agency currently assesses
salmon numbers using catch returns from anglers
and netsmen fishing in Christchurch harbour. The
netsmen, who are fishing for sea trout, record
and release all salmon they catch. Although netting
data provides information over part of the salmon
run, an additional system was needed to give a
complete picture.
Now, using special monitoring
equipment including hi-tech cameras, scientists
aim to accurately record the number of salmon
travelling up the Avon to spawn throughout the
entire year.
The equipment has been installed
at Knapp Mill near Christchurch where fish movements
are being closely monitored 24 hours a day using
a purpose-built fish counting device and bank
of eight digital video cameras.
Any fish above a certain size
that pass through the counter are automatically
caught on camera together with the date and time.
The data is stored on a computer where images
of individual fish can be viewed. The system allows
scientists to calculate an approximate size of
the fish and for the species to be determined.
Since it was re-installed in
February, more than 200 salmon have been recorded
migrating up the Avon by the new equipment at
Knapp Mill.
The research has shown it is
not only fish that pass through the electronic
counter. While fine-tuning the equipment, Agency
scientist Jon Bilbrough saw the unmistakable image
of an otter on his computer screen.
‘I was rather surprised, but
also pleased to capture this unexpected visitor
on film. The presence of otters on the Avon is
a positive sign that the river is in good health,’
said Jon, who was appointed by the Environment
Agency at the end of 2005 to head-up the fish
monitoring project at Knapp Mill.
Ultimately, Jon aims to improve
the system so that Agency staff can directly access
the fish counter images and data remotely from
their office. He also plans to install a pair
of underwater video cameras that will make it
easier to distinguish between salmon and sea trout.
One major improvement is the
speed at which images can be retrieved. With earlier
systems a person had to watch hours of video to
find the image they were looking for. Now, footage
can be retrieved in seconds.
‘The early results from this
latest monitoring are very encouraging. Used in
conjunction with the data from rod and net catches,
it will be a very useful tool and should give
us a much better understanding of salmon stocks
on the Hampshire Avon,’ said Jon.
The results of the monitoring
including photographs of fish will shortly be
displayed on the website of the Royalty Fishery
whose anglers fish the Avon in the vicinity of
Knapp Mill.
